This invention relates to electric motors and in particular, to miniature p.m.d.c. motors with coils of armature windings connected in star configuration and to a star connector for achieving this connection.
While it is known to connect p.m.d.c. motors in star configuration, the star connector is usually a ring having terminals corresponding in number to the number of armature coils and fitted to the commutator by way of an insulating supporting sleeve which is pressed over the commutator brush contact surface, see for example, JP-U-4-64975. A major disadvantage of this construction is that the commutator must be made longer to accommodate the loss of brush contact surface occupied by the star connector. There is also the added possibility of causing damage to the brush contact surface when the star connector is pressed onto the commutator.
Thus, there is a need for a star connector which will not damage the commutator during assembly and which does not require the commutator to be modified.
Accordingly, the present invention provides a novel star connector and/or a motor incorporating such a connector.
Thus, according to a first aspect thereof, the present invention provides a star connected wound rotor for a miniature electric motor comprising: a shaft; an armature core fitted to the shaft and having a plurality of armature poles; a commutator having a plurality of commutator segments for making sliding contact with a brush assembly, the commutator being fitted to the shaft adjacent a first end of the armature core; a star connector; and a plurality of coils forming an armature winding, each coil being wound around an armature pole and being terminated on a segment of the commutator and on the star connector, characterized in that the star connector comprises a base of insulating material acting as a spacer and fitted to the shaft adjacent a second end of the armature core and a terminal ring of conductive material fitted to the base and having a plurality of terminals connected to the coils, thereby forming a star connected armature winding.
According to a second aspect thereof, the present invention provides a star connector for a miniature electric motor comprising a base of insulating resin material and a terminal ring of conductive material fitted to the base and having a number of terminals for connection of one end of the coils forming a rotor winding.
Also, in accordance with a third aspect, the present invention provides a star connector for electrically connecting together lead wires from coils of a wound rotor of a miniature d.c. electric motor, the connector comprising: a base for direct mounting onto a shaft of the rotor; and a conductive ring having terminals for termination of the lead wires; wherein the base has a central boss portion with a central opening for receiving the shaft, a wall extending radially from the boss, a skirt extending axially from the radially outer edge of the wall, a number of openings in the skirt and a number of buttresses formed on the wall and the base remote from the skirt but adjacent the openings, and wherein the conductive ring has a flat ring portion located against the wall of the base and supported by the skirt and having a number of terminals extending radially from the ring portion, each terminal having an axially U-shaped portion, the terminals extending through the openings in the skirt with the U-shaped portions located radially adjacent the buttresses.